1. Field of the Invention
The present invention relates to an analog gateway and more particularly to an analog gateway, which can be used externally or embedded with one of various analog devices, for interfacing an analog device with a local persistent storage device in a stand alone mode of operation, and, in a network mode of operation, enabling bi-directional communication between the analog device and one or more workstations over a digital communication network using standard communication protocols, the analog gateway configured with a pipelined architecture which allows the cost of the device to be greatly reduced.
2. Description of the Prior Art
Various communication systems are known for transmission of analog signals over networks. Probably the most commonly known is the plain old telephone system (POTS). Both voice and data transmissions are known to be transmitted using POTS. Unfortunately, POTS requires a dedicated phone line and can be quite expensive depending on whether long distance charges apply. Accordingly, there has been a trend to utilize public digital communications networks, such as the World Wide Web and the Internet. Examples of such systems are disclosed in U.S. Pat. Nos. 6,092,078 and 6,281,790 and published international application disclosed in U.S. Pat. Nos. 6,092,078 and 6,281,790 and published international application WO 01/78297 A2. Such systems are used in connection with analog monitoring devices, for example, for use in healthcare and home security systems to transfer data over the Internet but have various drawbacks.
More particularly, U.S. Pat. No. 6,281,790 discloses a home security system in which various types of home security monitors are connected to a security panel. The security panel includes a microprocessor; sufficient memory to run an operating system; and an embedded web server. Communication between the various sensors and the security panel is by way of an RS 485 port. Accordingly, the sensors connected to the security panel are restricted to two operating states. Not only is the system restricted to sensors with binary outputs, but also requires a relatively expensive microprocessor and sufficient memory storage to run an operating system, such as a Microsoft Windows or UNIX type operating systems.
U.S. Pat. No. 6,092,078 describes a system for monitoring data from various sensors by way of a web-browser. The system accordingly requires a relatively expensive microprocessor and sufficient memory to run a UNIX type operating system as well as a web-browser.
Published international application WO 01/78297 A2 discloses an interface device for use in converting analog signals to digital signals and transmitting the digital signals over a digital communication network. Unlike the systems disclosed in U.S. Pat. Nos. 6,092,078 and 6,281,790, the system disclosed in the published international application does not require an expensive microprocessor; a Microsoft Windows or Unix type operating system; or a web-browser. Rather the system disclosed in the published international application uses a relatively simple inexpensive digital signal processor (DSP) for processing analog signals for transmission over a digital network. The system includes a coder-decoder (CODEC) which includes an analog to digital converter as well as a digital to analog converter for signal conversion to enable bi-directional communication with analog devices connected to a digital network. The CODEC utilizes a pair of relatively inexpensive digital signal processors and a control processor. The system disclosed in the published international application is for use in a synchronous communication network and thus requires generation of the local clock signal and thus requires a local oscillator which increases the costs of the system and prevents it from interfacing with TCP/IP networks such as the Internet without the use of a separately supplied protocol converter box.
Accordingly, there is a need for an analog gateway for interfacing various analog devices with a public communication network in an asynchronous manner while at the same time eliminating the need for Microsoft Windows or UNIX type operating systems.